338 ON THE MILK-DENTITION OF THE KOALA. [Mar. 15, 



Male with an internal subgular vocal sac, and black uuptial ex- 

 crescences on the inner finger. 



From snout to vent 67 millim. 



Three specimens from Faro Island. 



EXPLAJSTATION OF PLATE XXVIII. 



Fig. 1. Lepidodactylus woodfordi, p. 334. 



1 a. . Lower view of foot ; multiplied 3 times. 



2. Typhlops aluensis, p. 336. Upper view of head ; multiplied 4 times. 



2 a. . Side view of head ; multiplied 4 times. 



2 b. . Lower view of head ; multiplied 4 times. 



2 c. . Lower view of tail. 



3. Bafrachylodes vertebralis, p. 337. 



4. Hyla lutea, p. 337. 



4, On the Milk-dentition of the Koala. 

 By Oldmeld Thomas. 



[Eeceived February 15, 1887.] 



Among the few remaining Marsupials in which no trace of a milk- 

 dentition has yet been found, the Koala {Phascolarctos cinereus) 

 occupies a prominent place, especially as in this animal the last pre- 

 molar, or pm.^ which among Marsupials is the only tooth that 

 ever has a milk predecessor, is unusually large and powerful, and 

 might have been therefore expected, as in the allied Phalangers, to 

 have a proportionally well-developed predecessor. 



At last, however, I have been able to find traces in the Koala of 



Head of young Eoala, showing milk-dentition ; natural size. 



just such a rudimentary milk-dentition as has been described in the 

 Thylacine by Prof. Flower', and showing, just as in that animal, 

 that the ancestors of the Koala have had, and that it has now lost, 

 the ordinary amount of tooth-change found in the great majority of 

 Marsupials. 



In two very young and hairless Koalas, four and five inches long 

 respectively, I find, on cutting open the side of the jaw, clear and 



1 Phil. Trans. 1867, p. 63. 



